Instructions
Finish the main storyline to unlock the Parchment Desert.
Return to the Fossil Guild and buy four Oasis Seeds. Oasis Seeds cost 20,000 gold per seed.
Talk to the elderly man wandering the Parchment Desert. The man will automatically take the seeds from your inventory and plant them in the desert. All four Oasis seeds must be planted before you can access the fossil excavation area of Parchment Desert.
Tap the "R" button to use the sonar tool on the upper screen of the Nintendo DS. Run to the location of any green blips seen on the radar. Press "A" to dig in that spot. There is a random chance the Vivosaur will be a Mihu.